Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$76.57	4.869%	$80.2982	$80.30	$80.30	$80.30
Purchase #2	$30.95	9.603%	$33.9221	$33.92	$33.90	$33.90
Purchase #3	$44.71	4.452%	$46.7005	$46.70	$46.70	$46.70
Purchase #4	$85.48	4.526%	$89.3488	$89.35	$89.35	$89.30
Purchase #5	$58.42	6.616%	$62.2851	$62.29	$62.30	$62.30
Purchase #6	$114.46	7.509%	$123.0548	$123.05	$123.05	$123.10
Purchase #7	$185.33	7.319%	$198.8943	$198.89	$198.90	$198.90
7 purchase totals =	$595.92		$634.5038	$634.50	$634.50	$634.50